1. Field of the Invention
The present invention relates to a locking-unlocking mechanism, which is used in a telescopic device comprising a plurality of pipes telescopically arranged, for locking and unlocking the pipes at times of extension and retraction.
2. Description of the Prior Art
Heretofore, telescopic mechanisms have been known which comprise a plurality of pipes telescopically arranged to be capable of constituting a columnar structure.
In conventional telescopic devices, engineers have devoted their efforts primarily to providing a locking-unlocking mechanism capable of simply and smoothly attaining reliable and firm connection between pipes during extension and disconnection of the connected pipes in retraction operation. In telescopic devices employing extension-retraction mode by means of fluid pressure, a locking-unlocking mechanism is not necessarily required. However, this mode has a problem of leakage of a fluid during extension. Accordingly, it is desired to provide a locking-unlocking mechanism between pipes.
Performance in connecting extended pipes together and disconnecting the connected pipes determines strength and stiffness of the pipes in extended state or reflects on rapid and smooth extension-retraction movement. Accordingly, the connection required to be firm and reliable and the disconnection is required to be tarried out rapidly and precisely. At the same time, a locking-unlocking mechanism is required to have a structure which is simple in view of cost and light weight, which is not susceptible to failure, and whose maintenance is easy in terms of durability. Of those which have heretofore been proposed, however, none is satisfactory.